Transducer



July 24, 1962 F. R. SCHEPMAN ET AL 3,046,360

TRANSDUCER Filed May 4, 1959 INVENTOR FELIX HOBERTSCHEPMA N CO WIT TEN BERG JOHANNES OTTO M CHAEL VAN LANGEN AGENT United States Patent Q 3,046,360 TRANSDUCER Felix Robert Schepman, Nico Wittenberg, and Johannes Otto Michael van Langen, all of Emmasingel, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed May 4, 1959, Ser. No. 810,856 Claims priority, application Netherlands May 5, 1958 7 Claims. ((31. 179-100.)

Our invention relates to transducers for use in a device for recording or reproducing, with the aid of a common recording or reproducing member, a groovelike record track in which two signals having different directions of vibration are recorded simultaneously. The transducer comprises at least two parts which are joined without a coupling piece, each of which parts is at least substantially sensitive only to one of the two directions of oscillation.

In a copending application a transducer is described in which two parts are joined together without a coupling piece, each of which parts is sensitive to only one of two directions of oscillation which aflords the advantage that the separation of, and the composition into a double information is effected in the converting element itself, so that a coupling element as used in known converting devices having two separate converting elements may be dispensed with. In the embodiments disclosed in that application, the converting element may be made of piezoelectric material in the form of tubular or plate-like bodies.

In many cases, more particularly if seignette salt is chosen as the piezo-eleetric material, the converting element may be built up in a simpler manner. In accordance with our invention, the parts can be made of piezoelectric material in the form of small rods in which the direction of the pieZo-electrically active axis is at right angles to the main surfaces of the rods provided with electrodes, and the parts, located side by side in the direction of their length, mechanically joined together. The location of the main surfaces should be such that the active axes of the parts sensitive to the one signal are rotated through a given angle, preferably through 90, with respect to the active axes of the parts sensitive to the other signal.

In one practical embodiment of the invention, the converting element has a rectangular cross-section and comprises three parts, each also having a rectangular crosssection such that the joined separating surfaces between the three parts have a T-shape of cross-section. In the two parts located on each side of the vertical limb of the T the direction of the piezo-electrically active axis should have the same sense and the direction of the active axis in the third part should be at right angles thereto.

In another embodiment of the invention, the converting element also has a rectangular cross-section and comprises four parts each of rectangular cross-section such that the joint separating surfaces between the four parts have a cross-shaped cross-section. The two parts sensitive to the one signal should be located side by side with respect to their piezo-electrically active axes and the other two parts should be located one above the other.

In the last-mentioned case, it is advantageous for the direction of the piezo-electrically active axes in each pair of associated parts to be chosen of opposite sense. By suitably app-lying or deriving the two signal voltages, the converting element obtained has a voltage sensitivity which is doubled.

The distance between the main surfaces is preferably chosen to be equal in each part, since in this case the electrical capacitance of each part is the same.

The invention will now be described with reference to the accompanying drawing, in which corresponding parts are indicated by the same reference numerals and in which:

FIG. 1 shows a converting element comprising three parts each having a rectangular cross-section;

FIG. 2 shows a converting element comprising four parts each of rectangular cross-section, in which the directions, of the piezo-electrically active axes have the same sense, and

FIG. 3 is a variant of FIG. 2 in that the directions of the pieZo-electrically active axes in each pairs of associated parts are of opposite sense;

FIG. 4 shows a transducer in which the converting element according to the invention is employed, and

FIG. 5 is an elevation view of the transducer shown in FIG. 4.

Referring now to FIG. 1, reference numeral 1 indicates a converting element comprising three parts 2, 3 and 4 which are joined without a coupling piece. Each part, at least substantially, is sensitive only to one of the two directions of oscillation and is provided with electrodes 5 to 9, extending in the direction of the length of the element, for supplying or deriving the signal voltages. As shown in FIG. 1, the one signal (the x-signal) is applied between the electrodes 5, 6 and the other signal (the y-signal) is applied to the electrode 8 on the one hand, and one or both electrodes 7, 9 on the other. According to the invention, the parts 2, 3 and 4 are of piezo-electric material in the form of small rods in which the direction of the piezo-electrically active axes is at right angles to the main surfaces of the rods provided with electrodes and which, located side by side in the direction of length, are glued together. The location of the main surfaces is such that the active axis of the part 2, which is sensitive to the x-signal, is rotated through an angle of with respect to the axes of the parts 3, 4 which are sensitive to the y-signal. As may be seen further from the figure, the converting element 1 has a rectangular (square) cross-section and the three parts 2, 3 and 4 likewise have rectangular cross-sections such that the joint separating surfaces between the three parts have a T-shaped cross-section. In the two parts 3 and 4 located on each side of the vertical limb of the T, the direction of the piezo-electrically active axes is of the same sense and the direction of the active axis in part 2 is at right angles thereto.

In FIG. 2, the converting element 1 likewise has a rectangular (square) cross-section and is constituted by four parts 10, 11, 12 and .13 each of which likewise has a rectangular (square) cross-section such that the joint separating surfaces between the four parts have a crossshaped cross-section. The two parts 10, 11 'which are sensitive to the x-signal, are located side by side with respect to their piezo-electrically active axes and the two parts '12, 13, which are sensitive to the y-signal, are located one above the other. The direction of the piezoelectrically active axes in each pair of associated parts is of the same sense. The x-signal is connected to the electrodes 5 and 6 and the y-signal is connected to the electrodes 8 and 7 and/ or 9.

The converting element shown in FIG. 3 corresponds to that of FIG. 2, the only difference being that the directions of the pieZo-electrically active axes in each pair of associated parts are of opposite sense. The x-signal is therefore connected to the electrodes 5, 6 and the y-signal is connected to the electrodes 7, 9. The voltage-sensi tivity of the converting element is thus redoubled with respect to that shown in FIG. 2.

In all the embodiments of the rod-shaped converting element, the distance between the main surfaces in each part is preferably chosen to be equal so that advantage may be taken of the fact that the electrical capacitance in each part is the same.

FIG. 4 shows a converting device for recording or scanning by means of a common recording and scanning member 14, of a groove-like record track in which two signals (x and y) are simultaneously recorded with different directions of oscillation. Reference numeral 1 indicates the converting element which is supported in the casing of the device by means of a clamping body 15 and a suspension body 16 and which is provided with a body 17 for joining a member holder 18 carrying a recording or reproducing member 14 to the converting element.

FIG. is an elevation view of the converting device shown in FIG. 4, in which arrows 19 and 20 indicate the directions in which the converting element 1 is loaded by the action of one of the two directions of oscillation.

While we have described the invention in connection with specific embodiments other modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim is:

1. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising a plurality of rods of piezo-electric material, each of said rods having a piezo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their principal surfaces positioned so that the piezoelectrically active axis of a rod associated with one signal forms an angle with respect to the active axis of a rod associated with the other signal.

2. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising at least two rods of piezo-electric material, each of said rods having a pieZo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their principal surfaces positioned so that the piezo-electrically active axis of a rod associated with one signal forms an angle of 90 with respect to the active axis of a rod associated with the other signal.

3. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element of rectangular crosssection for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising three rods of piezoelectric material, each of said rods having a rectangular cross-section and a piezo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their principal surfaces positioned with the adjoining surfaces forming a T and the piezo-electrically active axes of the rods associated with one signal forming an angle with respect to the active axes of the rods associated with the other signal.

4. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element of rectangular cross-section for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillations and for converting a composite signal into two oscillations each having a different direction, said element comprising three rods of piezo-electric material, each of said rods having a rectangular crosssection and a piezo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their adjoining surfaces forming a T, the rod forming the crossarm of the T being associated with one signal, and the other two rods whose adjoining surfaces form the vertical stem of the T being associated with the other signal, the piczoelectrically active axis and the latter two rods extending in the same sense and direction and at right angles to the piezo-electrically active axis of said first mentioned rod.

5. A transducer for selectively recording and reproducing oscillations corresponding to variations in two dilferent directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element of rectangular cross-section for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising four rods of piezoelectric material, each of said rods having a rectangular cross-section and a piezo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their adjoining surfaces forming a cross and principal surfaces positioned so that the piezo-electrically active axes of the rods associated with one signal form an angle with respect to the active axes of the rods associated with the other signal.

6. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element of rectangular cross-see tion for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising four rods of piezoelectric material, each of said rods having a rectangular cross-section and a piezo-electrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their adjoining surfaces having a cross-shaped cross-section and with their principal surfaces positioned so that the piezo-electrically active axes of one pair of rods associated with one signal being parallel to one another and extending in the same sense in the same direction, the piezoelectrically active axes of the other pair of rods associated with the other signal being at right angles to the axes of the first pair and extending in the same sense in that direction.

7. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said varia- 5 tions, and an element of rectangularcross-section for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into tWo oscillations each having a different direction, said element comprising four rods of piezo-electric material, each of said rods having a rectangular cross-section and a piezoelectrically active axis which is at right angles to a principal surface provided with an electrode extending in the length direction of the rod, said rods being mechanically joined together with their adjoining surfaces having a cross-shaped cross-section and with their principal surfaces positioned so that the piezo-electrically active axes of one 6 pair of rods associatedwith one signal extending in opposite senses parallel to one another, the piezo-electrically active axes of the other pair of rods associated with the other signal being at right angles to the axes of the first 5 pair and extending in opposite senses in that direction.

References Cited in the file of this patent UNITED STATES PATENTS Williams Apr. 13, 1948 2,444,590 Bokeny July 6, 1948 2,775,460 Shivack Dec. 25, 1956 2,858,373 Hollrnann Oct. 28, 1958 

